/*- * Copyright (c) 2003, 2004 Lev Walkin . All rights reserved. * Redistribution and modifications are permitted subject to BSD license. */ #include #undef ADVANCE #define ADVANCE(num_bytes) do { \ size_t num = num_bytes; \ ptr = ((const char *)ptr) + num; \ size -= num; \ consumed_myself += num; \ } while(0) #undef RETURN #define RETURN(_code) do { \ asn_dec_rval_t rval; \ rval.code = _code; \ if(opt_ctx) opt_ctx->step = step; /* Save context */ \ if(_code == RC_OK || opt_ctx) \ rval.consumed = consumed_myself; \ else \ rval.consumed = 0; /* Context-free */ \ return rval; \ } while(0) /* * The BER decoder of any type. */ asn_dec_rval_t ber_decode(const asn_codec_ctx_t *opt_codec_ctx, const asn_TYPE_descriptor_t *type_descriptor, void **struct_ptr, const void *ptr, size_t size) { asn_codec_ctx_t s_codec_ctx; /* * Stack checker requires that the codec context * must be allocated on the stack. */ if(opt_codec_ctx) { if(opt_codec_ctx->max_stack_size) { s_codec_ctx = *opt_codec_ctx; opt_codec_ctx = &s_codec_ctx; } } else { /* If context is not given, be security-conscious anyway */ memset(&s_codec_ctx, 0, sizeof(s_codec_ctx)); s_codec_ctx.max_stack_size = ASN__DEFAULT_STACK_MAX; opt_codec_ctx = &s_codec_ctx; } /* * Invoke type-specific decoder. */ return type_descriptor->op->ber_decoder(opt_codec_ctx, type_descriptor, struct_ptr, /* Pointer to the destination structure */ ptr, size, /* Buffer and its size */ 0 /* Default tag mode is 0 */ ); } /* * Check the set of >> tags matches the definition. */ asn_dec_rval_t ber_check_tags(const asn_codec_ctx_t *opt_codec_ctx, const asn_TYPE_descriptor_t *td, asn_struct_ctx_t *opt_ctx, const void *ptr, size_t size, int tag_mode, int last_tag_form, ber_tlv_len_t *last_length, int *opt_tlv_form) { ssize_t consumed_myself = 0; ssize_t tag_len; ssize_t len_len; ber_tlv_tag_t tlv_tag; ber_tlv_len_t tlv_len; ber_tlv_len_t limit_len = -1; int expect_00_terminators = 0; int tlv_constr = -1; /* If CHOICE, opt_tlv_form is not given */ int step = opt_ctx ? opt_ctx->step : 0; /* Where we left previously */ int tagno; /* * Make sure we didn't exceed the maximum stack size. */ if(ASN__STACK_OVERFLOW_CHECK(opt_codec_ctx)) RETURN(RC_FAIL); /* * So what does all this implicit skip stuff mean? * Imagine two types, * A ::= [5] IMPLICIT T * B ::= [2] EXPLICIT T * Where T is defined as * T ::= [4] IMPLICIT SEQUENCE { ... } * * Let's say, we are starting to decode type A, given the * following TLV stream: <5> <0>. What does this mean? * It means that the type A contains type T which is, * in turn, empty. * Remember though, that we are still in A. We cannot * just pass control to the type T decoder. Why? Because * the type T decoder expects <4> <0>, not <5> <0>. * So, we must make sure we are going to receive <5> while * still in A, then pass control to the T decoder, indicating * that the tag <4> was implicitly skipped. The decoder of T * hence will be prepared to treat <4> as valid tag, and decode * it appropriately. */ tagno = step /* Continuing where left previously */ + (tag_mode==1?-1:0) ; ASN_DEBUG("ber_check_tags(%s, size=%ld, tm=%d, step=%d, tagno=%d)", td->name, (long)size, tag_mode, step, tagno); /* assert(td->tags_count >= 1) May not be the case for CHOICE or ANY */ if(tag_mode == 0 && tagno == (int)td->tags_count) { /* * This must be the _untagged_ ANY type, * which outermost tag isn't known in advance. * Fetch the tag and length separately. */ tag_len = ber_fetch_tag(ptr, size, &tlv_tag); switch(tag_len) { case -1: RETURN(RC_FAIL); case 0: RETURN(RC_WMORE); } tlv_constr = BER_TLV_CONSTRUCTED(ptr); len_len = ber_fetch_length(tlv_constr, (const char *)ptr + tag_len, size - tag_len, &tlv_len); switch(len_len) { case -1: RETURN(RC_FAIL); case 0: RETURN(RC_WMORE); } ASN_DEBUG("Advancing %ld in ANY case", (long)(tag_len + len_len)); ADVANCE(tag_len + len_len); } else { assert(tagno < (int)td->tags_count); /* At least one loop */ } for((void)tagno; tagno < (int)td->tags_count; tagno++, step++) { /* * Fetch and process T from TLV. */ tag_len = ber_fetch_tag(ptr, size, &tlv_tag); ASN_DEBUG("Fetching tag from {%p,%ld}: " "len %ld, step %d, tagno %d got %s", ptr, (long)size, (long)tag_len, step, tagno, ber_tlv_tag_string(tlv_tag)); switch(tag_len) { case -1: RETURN(RC_FAIL); case 0: RETURN(RC_WMORE); } tlv_constr = BER_TLV_CONSTRUCTED(ptr); /* * If {I}, don't check anything. * If {I,B,C}, check B and C unless we're at I. */ if(tag_mode != 0 && step == 0) { /* * We don't expect tag to match here. * It's just because we don't know how the tag * is supposed to look like. */ } else { assert(tagno >= 0); /* Guaranteed by the code above */ if(tlv_tag != td->tags[tagno]) { /* * Unexpected tag. Too bad. */ ASN_DEBUG("Expected: %s, " "expectation failed (tn=%d, tm=%d)", ber_tlv_tag_string(td->tags[tagno]), tagno, tag_mode ); RETURN(RC_FAIL); } } /* * Attention: if there are more tags expected, * ensure that the current tag is presented * in constructed form (it contains other tags!). * If this one is the last one, check that the tag form * matches the one given in descriptor. */ if(tagno < ((int)td->tags_count - 1)) { if(tlv_constr == 0) { ASN_DEBUG("tlv_constr = %d, expfail", tlv_constr); RETURN(RC_FAIL); } } else { if(last_tag_form != tlv_constr && last_tag_form != -1) { ASN_DEBUG("last_tag_form %d != %d", last_tag_form, tlv_constr); RETURN(RC_FAIL); } } /* * Fetch and process L from TLV. */ len_len = ber_fetch_length(tlv_constr, (const char *)ptr + tag_len, size - tag_len, &tlv_len); ASN_DEBUG("Fetching len = %ld", (long)len_len); switch(len_len) { case -1: RETURN(RC_FAIL); case 0: RETURN(RC_WMORE); } /* * FIXME * As of today, the chain of tags * must either contain several indefinite length TLVs, * or several definite length ones. * No mixing is allowed. */ if(tlv_len == -1) { /* * Indefinite length. */ if(limit_len == -1) { expect_00_terminators++; } else { ASN_DEBUG("Unexpected indefinite length " "in a chain of definite lengths"); RETURN(RC_FAIL); } ADVANCE(tag_len + len_len); continue; } else { if(expect_00_terminators) { ASN_DEBUG("Unexpected definite length " "in a chain of indefinite lengths"); RETURN(RC_FAIL); } } /* * Check that multiple TLVs specify ever decreasing length, * which is consistent. */ if(limit_len == -1) { limit_len = tlv_len + tag_len + len_len; if(limit_len < 0) { /* Too great tlv_len value? */ RETURN(RC_FAIL); } } else if(limit_len != tlv_len + tag_len + len_len) { /* * Inner TLV specifies length which is inconsistent * with the outer TLV's length value. */ ASN_DEBUG("Outer TLV is %ld and inner is %ld", (long)limit_len, (long)tlv_len); RETURN(RC_FAIL); } ADVANCE(tag_len + len_len); limit_len -= (tag_len + len_len); if((ssize_t)size > limit_len) { /* * Make sure that we won't consume more bytes * from the parent frame than the inferred limit. */ size = limit_len; } } if(opt_tlv_form) *opt_tlv_form = tlv_constr; if(expect_00_terminators) *last_length = -expect_00_terminators; else *last_length = tlv_len; RETURN(RC_OK); }